A vehicle launch is a low-speed drive-away event in which a vehicle with a transmission is accelerated in response to the vehicle operator depressing an accelerator pedal. When the vehicle powertrain is equipped with a conventional automatic transmission, launch behavior is largely regulated by the torque converter, which ultimately sets engine speed and wheel torque as a dynamic function of engine torque. In such a setting, the torque converter characteristics are first engineered to trade off fuel economy and driving performance, then engine pedal maps (the engine control software relationship between accelerator pedal position and engine torque) are tuned to provide the best vehicle feel for the given converter design. The torque converter thus transmits available engine torque to the transmission to smoothly bring engine and transmission input speeds together while accelerating the vehicle mass.
An emerging trend in automatic transmission design eliminates the torque converter and replaces it with an automatically controlled clutch. Such transmissions provide a lower number of parts, simplicity and robust design, and much commonality with manual transmissions, potentially facilitating production. Such a change further enables the use of algorithms that can control the clutch in ways that may eliminate or reduce some of the design tradeoffs inherent in the passive torque converter system.
Vehicle operators may have expectations for vehicles without a torque converter to behave similar to what they are used to in vehicles with a torque converter. The inventors herein have recognized these issues, and have developed systems and methods to at least partially address the above issues. In one example, a method comprises controlling a capacity of a clutch configured to transmit torque between an engine and a transmission, and an output of an electric motor positioned in a driveline of the hybrid vehicle during a vehicle launch to emulate a performance of a torque converter positioned in the driveline of the hybrid vehicle, under conditions where the hybrid vehicle does not include the torque converter. In one example of the method, the transmission comprises a dual clutch transmission. In this way, vehicle operator expectations for vehicle launch behavior may be met for vehicles that do not include a torque converter, such as vehicles that include an electric motor in the vehicle driveline and at least a clutch configured to transmit torque from the engine to one or more wheels via the transmission.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.